


PERIHELION.

by petalgrown



Category: Katekyou Hitman Reborn!
Genre: (there are many different ways to love), Alternate Universe - Canon Divergence, Alternate Universe - Siblings, Family Feels, Fix-It, Flame Lore (Katekyou Hitman Reborn!), Gen, LGBTQ Themes, M/M, Self-Indulgent, Slow Burn, Team as Family, Worldbuilding
Language: English
Status: In-Progress
Published: 2021-03-06
Updated: 2021-03-06
Packaged: 2021-03-19 10:41:08
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,113
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29873415
Author URL: https://archiveofourown.org/users/petalgrown/pseuds/petalgrown
Summary: —the point in the orbit of a planet, asteroid, or comet at which it is closest to the sun.The thing about Mitsuki is that he’s always been a curious and stubborn person, even when he was younger—especially when he was younger. He learned his father was hiding something and didn’t stop until he knew what it was.(or tsuna has an older brother, and this does not change the fact that he is slated to become a mafia boss. it does change some things, however)
Relationships: Dino (Katekyou Hitman Reborn!)/Original Male Character(s), Sawada Nana & Original Character(s), Sawada Tsunayoshi & Original Character(s), Vongola Tenth Generation Guardians & Original Male Character(s)
Comments: 1
Kudos: 16





	PERIHELION.

**Author's Note:**

> back at it again with the unapologetically self-indulgent khr fics and no one can stop me. i really adore writing sibling and family dynamics in general, so here i am with a different take.
> 
> starting off so there isn't any confusion, mitsuki is 21 at the fic's start and is in college because i think there should be more college aged ocs having to deal with whatever canon throws at people. i've had the concept of him rolling around in my head for months so finally glad to share!!
> 
> this is a big ol' au in general and once again me playing around in the piles of empty space khr left us and stirring up some things in canon i didn't care for. will go into a little more detail of what's going on at the end. but also note this fic starts in medias res since starting at the very beginning isn't what i felt like doing for this!
> 
> anyways!!! please enjoy!  
> (i will tackle any lingering mistakes at a later date)

Mitsuki is not a fan of the winter and doesn’t think he ever will be.

A wilting flower as soon as the weather starts to drop is one of his mother’s favorite facts about him; fondly spoken when she would wrap an extra scarf around his neck or place a cup of tea in his hands. 

It’s not something he can help, so it’s easily accepted by most people that know him for long enough. The sky is blue. The Earth spins. Sawada Mitsuki struggles with bare minimum functioning as soon as December rolls around. 

This is ironic considering that it’s December now and yet he isn’t warm in his apartment tucked under the _kotatsu_. He doesn’t have any more classes for the day and work won’t roll around until tomorrow. He could easily use the rest of the hours in the day to take a nap or catch up on any coursework due this week, but his priorities have been swapped around since this morning when his mother called and insisted he come over to visit and have dinner. She’d be making one of his favorites tonight, and Mitsuki isn’t stubborn enough to pass up a home-cooked meal with guaranteed leftovers to take back with him. 

Her words were spring cheerful and held some excitement that’s been steadily increasing in her tone lately which also meant he’d feel bad for denying her specific request, besides.

The word is Reborn has a visitor over to help Tsuna for a bit. And usually, when Mitsuki learns the hitman has his hands mixed in something, he always feels less inclined to help deal with it. He’s avoided a majority of tutoring antics by virtue of not living in the Sawada household anymore, but there have been times when Mitsuki has had to bring an extra pair of clothes for his younger brother and put ointment on bruises and minor burns. 

The only constant adult the kids have with them at any given time is Reborn, which isn’t a bad thing, and Namimori is relatively calm compared to most places. It’s just a little concerning at times, but if Nana is more excited than anything about whoever this visitor is, then maybe them being around isn’t so bad. 

It’s what Mitsuki silently prays for when he gets closer and closer to his childhood home, at least. The route now muscle memory from years of walking down the familiar streets and passing the shops that have changed very little over years. It’s nice to know that some things stay the same no matter how strange life might get. 

Though while it’s all the same doesn’t mean there aren’t differences to be noticed. It’s a small one he catches as he walks through the neighborhood. One that most people probably wouldn’t pick up on unless they lived in this particular area for an extended period of time—not many people are out, is the thing. Which is strange given the fact that the time of day is perfect for the regular gardeners to be tending to their plants even more so since the changing in weather means winter prep is needed. He doesn’t even see children playing in the yards and along the sidewalk despite school being over—it’s cold, but not enough that the usual jacket won’t be able to handle.

It all feels tense in a way Mitsuki doesn’t like, and the feeling only grows worse as he gets closer and closer to home until he finally can spot the exact cause of the strange atmosphere throughout the neighborhood. 

He sees sleek black cars and broad-shouldered people dressed in finely pressed suits standing in front of his house. They’re on guard, that much he’s certain of, so that’s one immediate concern down. The second flash of irritation comes from how overt the whole thing is, and makes him wonder who the hell Reborn invited over. They might as well have put a flashing neon sign right above the house itself. 

Well, it can be dealt with as soon as he talks to the person, so Mitsuki speedwalks up towards the house. Or at least tries to and ends up failing because he gets stopped right before he reaches the gate. 

At least the guard is doing his job when he says, “Only authorized individuals may approach and enter the Sawada residence.”

They must not have all the information then. Mitsuki resists the urge to roll his eyes and snap since he isn’t in the habit of being rude to grunts that only know the bare minimum.

“I live here,” he says instead, arms crossed and posture straight. Technically, he hasn’t actually _lived_ with his mom and brother since he was eighteen and moved closer to the university, but semantics.

He doesn’t have much in the way of height being only 166 centimeters tall, but he’s learned over the years that confidence is often key. Especially when the mafia is involved. It almost seems to work too; the guard steps back just a little but catches himself at the last second with a head shake and a thin-lipped frown. 

“I don’t recognize you from the files and no one has reported seeing you enter or exit the house to confirm this fact.”

Definitely a lack of information then. Annoying to deal with, but also not the first time it’s happened to him. Mitsuki’s lost count of how many people tripped over themselves as soon as they realized or were told that he’s Iemitsu’s son. His dad did a good job at keeping his family status a secret outside of vague stories and overzealous praise. He will begrudgingly give the man credit for that much considering how high Iemitsu is on the mafia hierarchy.

At this point, Mitsuki knows there isn’t even a reason to pull out his ID, not with how easily they can be forged these days. Most mafioso worth their salt wouldn’t accept one under these circumstances anyway, and Mitsuki doesn’t make a habit of carrying around his other forms of identification even though he’s constantly told to by his father and Asahi. 

He’s still trying to keep some form of normality in his life since it seems to be rapidly dwindling as the days go by.

Instead, he pulls out his phone and punches in a few buttons. This isn’t a big deal and more so of a minor inconvenience than anything else. 

Reborn picks up on the third ring. His high-pitched voice is tinny over the speaker, “Ciaossu. What seems to be the problem this time, Mitsuki? Did Tsunayoshi whine to you about what happened today already?”

Mitsuki is speechless for a few seconds with his shock before sighing, “I don’t even know what you’re talking about. I’ll deal with that later, but first I need authorization to get into the house. I got stopped at the gate.” 

“I see. Hold on,” is the only response he gets before the other line goes silent for nearly an entire minute, “You should be cleared to get through now. 

Reborn hangs up without a proper goodbye like always and Mitsuki pockets his phone. The mafioso in front of him mutters into his earpiece, speaking Italian low enough that Mitsuki can’t catch what’s being said. But whatever it is seems to do the trick because he moves out of the way and bows a neat 90 degrees. 

“Apologies for the trouble, Sawada-sama,” the honorific is much too formal and feels added on with a last minute uncertainty as if the man doesn’t know the right one to use. He wouldn’t be surprised if that was the case but doesn’t have the energy to correct the potential mistake. 

Mitsuki sighs and is glad the apologies aren’t the frantic and awkward sort at the very least, “You were just doing your job, don’t worry about it.”

He slips through the gate and up to the door before anyone else can talk to him and unlocks it with what has to be fifteen different pairs of eyes staring at him the whole time. 

Good grief. 

Inside the house at least feels normal, relatively speaking considering recent events and unforeseen changes. But it looks the same and still carries the same subtle hint of the lavender candles Nana likes to burn. 

He sits down on the step to the _genkan_ and removes his boots before shouting into the house, “I’m home!”

The first person who greets him is Nana, a smile on her face and apron tied around her waist. Dinner must be big if she’s already started cooking now. 

“Welcome home, Micchan,” she coos and helps him take off his scarf and jacket to be put away in the coat closet, “You just missed Gokudera-kun and Yamamoto-kun about half an hour ago.”

“I’ll probably see Gokudera-kun later tonight,” he leans into the hug he gets, patting her back a few times before letting go, “Where are the other kids? Feels kinda quiet.”

“Bianchi-san took them to the park before dinner. Very sweet of her to do so,” Nana makes her way back into the kitchen. Mitsuki follows close enough so he can still hear her over the sound of the food cooking, “Good news! Kazuki-san called me this morning too. Him and his husband will be watching I-Pin this weekend.”

“Oh? Glad we finally got that sorted then,” more importantly it means I-Pin likes them enough to stay in their company for more than a few hours. The steadily increased exposure she’s had since she showed up in Namimori has helped, “Do you need me to drop her off or pick her up?”

“I’ll be dropping her off Friday afternoon, so you picking her up Sunday afternoon would be perfect,” Nana hums and resumes fussing over food. 

“That’s fine,” he probably won’t even have to adjust his work schedule. Hell, it might even factor into work hours or a pay bonus. The Hibaris might be the scariest family in this part of Japan, but at least they know how to treat their employees, “Where’s Tsu-kun and the mysterious guest you’ve told me nothing about?”

Nana giggles, stirring whatever’s in a pot, “Upstairs doing who knows what besides waiting for dinner with Reborn-san. Go say hello. I’ll call you all down when it’s finished.”

It’s a Nana-brand dismissal, so Mitsuki takes it and doesn’t linger. He walks up the steps two at a time, noting cracks in the railing but at least it seems to be sturdy enough. For now anyway; there are too many kids in the house these days for faulty handholds especially when factoring in Tsuna’s innate clumsiness. 

He walks past his old bedroom, now converted into a guest bedroom out of necessity, the bathroom that he and Tsuna used to share, and doesn’t bother knocking as he opens the door to his brother’s room. It doesn’t work—there’s resistance, a muffled thud, and a familiar yelp. 

Mitsuki rolls his eyes, “Move out the way of the door, Tsuna.”

“No,” the voice on the other side is familiar in its muffled petulance, “You didn’t knock.” 

He sighs, deems it a fair enough compromise, and knocks three times. Tsuna opens the door to his room barely seconds later, pouting and rubbing at the back of his head. 

“Did that actually hurt?” he drawls and pokes at the beginnings of a bruise blooming on his younger brother’s cheek. 

Tsuna yelps again and bats his hand away with what’s practically a whine. He doesn’t know where this kid got his dramatic side from, probably Iemitsu, all things considered. 

“Stop bullying me! Are you coming in or not?”

“There’s a guest,” Mitsuki shrugs, “mom said I should visit.”

Tsuna sighs as if letting Mitsuki into his room is a great feat, but scoots out of the way regardless to let him walk in. It’s messier than the last time he was here is what he notes first. The second thing is the vaguely familiar blond sitting on the floor at the small table staring at them and looking amused. The third thing is that Reborn is doing gun maintenance which is always strange to see. 

“Dino-san, this is Mitsuki-nii,” Tsuna at least introduces, but he doesn’t seem enthusiastic about it, “Mitsuki-nii, Dino-san. He’s an old student of Reborn’s.”

Realization hits after introductions are done, and Mitsuki plops down on Tsuna’s bed to get comfortable.

“Cavallone, right?” he wonders if Iemitsu knows, and thinks more than likely. 

Dino looks pleasantly surprised. Tsuna being naive to the mafia must have already painted a picture, “You’ve heard of me?”

It’s Reborn who answers, “Unlike Tsunayoshi, Mitsuki has already been exposed for some odd years now. Of course he knows of you. I’d be disappointed if he didn’t.”

“I hate being reminded of that,” Tsuna mutters, taking a seat on the bed next to Mitsuki.

“You hate being reminded that dad’s in the mafia too,” not that Mitsuki can blame him. It took a while for him to wrap his head around the information as well when he first learned. 

“Well, he is pretty good at keeping secrets,” Dino pipes up. His smile is practically charming. Elbow resting on the table as it is and cheek cradled against palm grants Mitsuki a clear view of the tattoos snaking up his arm and across his hand, “Everyone knows he at least has one kid. I expected just Tsuna. I’m sure some people just expect Mitsuki.”

Dino isn’t wrong about the secret keeping part. For all of Iemitsu’s blustering at times, which has to be an act on most days, he really did keep the mafia thing hidden rather well. A surprise considering how flimsy his actual cover story was. It probably would have stayed if Mitsuki didn’t get nosy and go poking where he absolutely shouldn’t have all those years ago, but he’s always been a curious and stubborn sort. Often told he’s lucky it hasn’t led him into too much trouble yet. 

“And we want to keep it that way,” Mitsuki smiles and his tone turns saccharine sweet, “You’re making that hard to do, Don Cavallone. Fix it before the Hibaris have to get involved.”

The blond looks genuinely confused, Mitsuki again resists the urge to roll his eyes. 

“Your people are loitering in the streets. It’s painfully obvious that something suspicious is going on here.”

“Oh! Oh, that! Sorry, they’re insistent. I told them I don’t need the extra protection but…I think they’re worried honestly. It was hard to get concrete information about Namimori, so this is their way of being extra careful,” he looks sheepish, tattooed hand now used to rub at the back of his neck. 

“Namimori is safe,” Mitsuki reassures. He can never properly explain how it is because that’s complicated; it just is, “Where are you even staying?”

“Here,” Tsuna states briefly looking up from the manga he started reading, “He’s been sleeping in the other guest bedroom. I don’t know where all his people go at night, but they’re always hanging around in the morning.”

This isn’t surprising given that Nana loves having guests over and Reborn is an agent of chaos stuck inside a toddler-sized body. Mitsuki feels a headache coming on worse than when it was agreed that Reborn would be living right under the roof. 

“Get a hotel,” he doesn't mean for his affect to be so flat. It always makes him sound meaner than he actually is. 

Dino looks scolded, good, not his intention, but good, “I don’t know of any hotels that would be so...accommodating. Like I said, getting information about Namimori was harder than my team expected.” 

There’s the familiar sound of gun mechanisms clicking into place before Reborn says, “Even so, information gathering is a good eighty percent of the job. I taught you better than to waltz into new territory without having all your bases covered."

Dino, to Mitsuki's surprise, actually pouts, cheeks glowing faintly red with what he assumes is from embarrassment. Weird for a mafia boss, he decides, or maybe it’s just the company. 

“I work at a hotel specifically for this sort of stuff," Mitsuki admits easily because Dino getting a hotel would be better than him crashing at his family’s house. Besides, it's good for business, "Get one of your people to book at the Silver Crane, preferably your second in command if they’re here. You can use the Cavallone name and tell them that Mitsuki recommended the place.” 

Dino starts scrambling to do just that. Mitsuki rolls his eyes and pulls out his phone. 

> **Mitsuki:** let one of your dads know that the hotel is getting important visitors from italy  
>  **Mitsuki:** they might be staying for a while  
>  **Kyouya:** I’m not your errand boy.

Tsuna, nosy kid that he is, peeks over Mitsuki’s shoulders to start reading the messages, leaning his weight on Mitsuki’s arm. 

“Kinda weird that you know Hibari-senpai enough to just text him like that.”

He elbows his brother gently for more room to maneuver, “I’ve been working for his dads since I was fifteen. It’s not that weird,” part of that work also involved what could have only amounted to babysitting and making sure Kyouya didn’t beat up too many people in a day after elementary school.

Not weird at all if you take the Hibari family into account. 

> **Kyouya:** Asahi said if they miss check-in time then they’re sleeping outside. 

“If you miss check-in time then you have to sleep outside,” Mitsuki repeats while sending a quick _thanks_.

“I think it should be fine,” Dino lets out a nervous bit of laughter, “I talked to Romario, so he should be taking care of everything now.”

Mitsuki doesn’t know who Romario is, but figures he’s high enough up the line to be trusted with this. Either way, it’s no longer his problem. It wasn’t his problem to deal with in the first place, but considering that Reborn knows exactly where he works and didn’t bother mentioning it decidedly made it his to fix by proxy. 

With that potential issue taken care of, he falls back on the bed, nearly squishing Tsuna under him in the process. He gets a slap on the arm for his actions, and it doesn’t even sting a little. 

“I’m tired,” he huffs and adjusts himself so he’s facing the wall and shoves a pillow over his head, “Wake me up when dinner is ready.” 

There’s whispering about him as he dozes—asking if he’s ok and assurances that he is and it’s just the weather and coming here straight from classes. At least they’re polite enough to be quiet about it because it’s easy enough for Mitsuki to fall into a proper sleep. 

* * *

The process of waking up is not as gentle, however.

There's a sudden riot of noise, a sharp pain on his stomach that makes Mitsuki lurch up automatically only to have his head slam into something hard. Light bursts behind his eyelids and the sound of familiar, high pitched laughter can be heard mingled with whoever is groaning on the floor nearby. 

“Lambo-san did it! Lambo-san woke up Micchan-nii!” Mitsuki can feel the kid bouncing on the bed—at least it isn’t his stomach this time. 

“Thanks,” he grits out, rubbing his head until the pain recedes enough that he can get his eyes open. 

A glance to the floor reveals Dino was the other unlucky participant in this. Hopefully, he didn’t bite his tongue.

Mitsuki sighs, feeling defeated already, wanting to go back to sleep, “Is it time for dinner?”

Lambo stops his bouncing, changing gears to make a scrambled launch for Mitsuki’s lap. The kid’s advances are stopped by Mitsuki squeezing him into an impromptu hold disguised as a hug, but it’s accepted easily with a bubbling flow of laughter. 

“Mama says it’s time for dinner!” Lambo wiggles and crows, “Lambo-san was a good boy and woke you up before food got cold.”

“I see. I see,” he nods, adjusting his hold so he can get out of bed and not risk Lambo falling. Apparently, he bounces if dropped sometimes, but he doesn’t want to test that theory. Gokudera was the one that told him that anyway and sometimes that one is a brat, “Thank you for waking me up, but you have to remember to be gentle.”

Lambo stares at him with wide, green eyes, “Gentle?”

“Gentle,” Mitsuki repeats, extending his free hand to help Dino stand, “Bouncing on people’s tummies can hurt. If you wanna wake them up, try patting their shoulders or calling their names.”

“Did Lambo-san hurt Micchan-nii?” 

“Only a little,” turns out Dino is a good head taller than him, or just about, which isn’t surprising. At least it gives him a clear view of his chin without needing to twist his head this way and that. Mitsuki knows how hard his head is, fights with Tsuna, when they were younger, were a testament to that, “I’ll be fine though.” 

Dino, however, does not look convinced when he asks, “Are you sure?”

Mitsuki clicks his tongue, hiking Lambo up higher on his hip. The kid starts playing with the longer strands of his hair, but not tugging like he normally does, so Mitsuki lets him be, “You’re going to bruise though. Do you trust me?”

At least Dino doesn’t answer immediately, contemplating the question with an uncertain look on his face. Reborn might even be proud, self-preservation instincts, or something like that. He’s always muttering about kids these days not having any. 

“I...don’t even know you?”

“Hah! Good answer,” Mitsuki smiles, “You can trust that I’m not stupid enough to hurt you right in my brother’s room while I’m holding a toddler and thirty of your men are right outside.”

Dino shrugs; he tries to smile as well, but ends up wincing, “When you put it that way, sure.”

The thing about Mitsuki is that he’s always been a curious and stubborn person, even when he was younger—especially when he was younger. He learned his father was hiding something and didn’t stop until he knew what it was. He learned the Sawadas have an inclination for flickering flames and didn’t stop until he learned how to light one in the palm of his hand. 

It takes focus, as it always does, with the help of the bracelet he wears. Flame conductive and a gift from Iemitsu, unassuming in its appearance; his father always avoids telling him where or how exactly he got it. It’s the one secret Mitsuki will let lie.

His flame isn’t the biggest or the strongest, but it’s enough for this. He needs practice anyway and bruises have always been the simplest things to heal. Reborn has barred him from using it on Tsuna, insisting that his brother doesn’t need to be coddled at every turn. Being raised as civilians has set them behind, but Tsuna even more so considering his age and the position he’s slated to fill.

Using it on Dino is a good excuse, and he doubts a _Don_ wants to explain getting hurt in such a silly way.

It’s only a few seconds of contact where Mitsuki had to rest his hand against the steadily appearing bruise on Dino’s face. He drops his hand as soon as it’s over and the sunshine yellow of the flame disappears. He smiles and nods when he sees that the damage has been mended. 

Lambo claps, cooing something about pretty lights and magic. Lambo is also the one who most often gets the treatment. Kids are clumsy and it helps Mitsuki with finer tuned control, anyway. 

“You should be good to go. Don’t worry if it itches for a bit, that’s normal,”

Dino nods looking a little dumbfounded and dazed. Mitsuki isn’t surprised; he isn’t secretive about the whole Flame thing but there’s a difference between knowing something and being able to do something. Most people he’s run into fall into the former category. 

They’ve dithered for too long; Lambo starts swinging his little legs and humming about dinner. He’ll make a break for it as soon as Mitsuki even moves an inch to put him down, so the hold on him stays. He doesn’t remember Tsuna being nearly this kinetic at this age—it feels like a learning curve. 

He turns and gets the door open, “C’mon, Dino-san, before they send someone else. Mama probably won’t let anyone eat without you there anyway.”

He gets a silent nod again but is followed without any sort of questions like he expects. 

Mitsuki raises an eyebrow and shakes his head. 

_Weird guy_ , he thinks and leads their party of three onward. 

**Author's Note:**

> and i hope you enjoyed that!!! i will list a couple of things to note since starting in the middle of things like that can leave people confused, i know!
> 
> — nana & iemitsu are older than their canon counterparts to adjust to the fact that mitsuki is 21. they're ranging in mid to late 40s  
> — hibari has two dads!!! asahi's family owns a hotel chain that mitsuki works at  
> — the "iemitsu in the mafia thing" was revealed much earlier. will go into detail about that later since that's what's affecting practically everything in this au  
> — mitsuki has sun flames  
> — yes! there is a pairing for this fic!! it will be slow burn due to the nature of things. i wanted to have fun and give the gay group of teens some older gays to look up to. gokudera and kyouya in particular end up flocking to mitsuki the most in different ways 
> 
> i think that's it for now! please don't hesitate to drop a comment if you can and please know i always appreciate them no matter what!!! i will see you guys next time!!


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